Pressure bar and pressure bar holder assembly in veneer cutting machines



Aug- 19, 1952 E. H. MERRI 2,607,378

TT PRESSURE BAR AND PR SURE BAR HOLDER ASSEMBLY Y IN VEN TING MACHINES Fi Aug. 25, 1948 FIG .3

A TTORNEY Patented Aug. 19, 1952 PRESSURE ABAR AND PRESSURE BAR Y HOLDER ASSEMBLY IN VENEER CUT- TING MACHINES Ericsson Merritt, Lockport, N. Y., assignor, by

mesney assignments, to Solem Machine Company, Rockford, Ill., a corporation of Illinois Application August 25, 1948, Serial No. 46,084.'y

This invention relates to the art of Acutting and Vslicing wood veneer; more particularly it relates to an improved pressure bar and pressure bar holder combination assembly 4to befused with veneer cutting andslicing equipment.

vInl general practice rotary veneer is produced by revolving a log against a knife whose length is equal to or in excess of the length of the log being cut. I Sliced vveneer is produced by clamping a flitch to a reciprocating table and moving the table with the flitch past the knife. At each stroke a sheet of veneer is cut from the iiitch. In each of the described veneer cutting operations, to prevent the wood from' splitting ahead of the knife, a pressure bar is provided to apply pressure tothe log just ahead of the knife. Thus, the ribbon of veneer severed from the log by the knife is actually extruded through the slot formed by the knife-and the pressure bar. The cross-section of this slot is slightly less than the thickness of veneer being cut. To

vcut smooth uniform thickness veneer, the slot must be of uniform cross-section and have parallel edges. Furthermore, in the case of rotary veneer the bottom edge of the slot formed byv the edge of the knife must be in accurate parallel relationship to the axis of rotation of the log and the top of the slot formed by the pressure bar must be in accurate parallel relationship to the knife edge. Since it is not unusual to cut veneer as thin as fteen-thousandths of an inch in thickness, it is obvious that the tolerances to which the pressure bar must be set, are

extremely narrow.

Pressure bars generally vary in size from l/2 inch to 3Ainch thick, usually 1/2 inch to 2 inches wide when new, and varying in length from 24 inches to .200 inches. Adjusting bolts are usually provided in orderthat the contact edge of the pressure bar maybe adjustably maintained in accurate parallel relationship with the cutting edge of .the knife. Such a light steel section as the pressure bar, will, if placed onedge and supported at both ends, deect appreciably due to its own weight-alone, not to mention the loading incident to the-cutting of veneer. As the pressure bar becomes narrower due to grinding, this. deflection materially increases. Thus, the pressure bar itself hasv little inherent rigidity when considered as a beam.

Pressure bars contain a considerable amount of internal stresses. Additional stresses are built up in theedge of the pressure bar by the constant peening action ofy the log striking'the pressure bar. Ihis is particularly. tru'e when virregularshaped logs are being reduced to a cylinder preliminary to the cutting of veneer. Preparatory to a grinding or sharpening operation on the pressure bar, due to the stresses introduced by v the veneer cutting operation, it is necessary to force the pressure bar to assume a straight line. The bevel of the pressure bar is ground until a sharp contact edge is produced'which is a straight line within the limits of accuracy of the grinder and the perfection of the plane of the face of the pressure bar. This grinding operation to a certain extent releases many of the stresses which `were formed in the pressure bar during the cutting operation. When'the presl sure bar is released from the Vgrinder clamps whichA hold the pressure .bar rigidly .in vplace during the grinding operation, it immediately assumes its natural shape and the contact edge is no longer a true straight line. Accordingly, when this pressure bar is attached to Ythe pres- -sure bar-carriage in the veneer cutting machine, Vit must be adjusted. to compensate for the width lost in the grinder and also it must be forced by local adjusting screws provided in the pressure bar carriage, totake such a shape Vthat the contact edge will be a truer straight line parallel to the axis of rotationof the log. This is a time consuming operationr requiring a high degree 'of skill. Thus, according to the method as practiced heretofore of handling veneer cutting pressure bars, a precision alignment of the pressure bar is required for both the grinding operation and for the repositioning of the sharpened pressure bar in its holder on the cutting machine.

It is an object of this invention to provide a pressure bar and pressurer bar holder assembly which facilitates the positioning of the pressure barin a veneer cuttingmachine so that precision alignment is obtained with a minimum amount of local adjusting.

Another object of this invention is to provide apressure bar and pressure bar holder assembly which pressure bar, when precision ground, will' be in perfect alignment without further adjustment when placed in the veneer cutting machine.

It is also an object of this invention to provide an improved pressure bar and pressure bar holder assembly for a veneer cutting machine which eliminates all but a small fraction of the time required to change a pressure bar in a'veneer lathe or a veneer slicer.

Further yobjects will become apparent from the descriptionA of the invention and the claims.

These objects are accomplished by means of the applicants invention herein described, which provides an accurately machined rigid steel beam, called the holder, to which a pressure bar is adjustably attached. 'I'he holder is so constructed as to have a moment of inertia sufciently great to resist deflection of the pressure barcause'd b y unbalancedy stresses therein. The pressure barand pressure bar holder are removable as a unit from the veneer cutting machine. Threaded holes are provided in the holder whereby the pressure bar may be securely held thereto. Push and pull adjusting screws are also provided for in the'h'older to facilitate adjustment of the pressure bar in the holder. The machined surfaces of the 'holderland their cooperative machined surfaces on the Veneer cutting machine are so constructed aste main# tain a fixed relationship between the surfaces` accommodate an Allen wrench whereby the eri-J tire pressure bar holder 4 is securely fastened Vto the pressure bar holder carriage 8. Pressure VVcutting knife I 9 cutting a sheet of veneer which isextruded through the slot one side of whichis fo'rmed'bylthe knife edge 2| and the otherr side of which is formed by the edge of pressure bar I4, held in place by pressure bar holder 4. On .requiring resharpening, the pressure bar and the line of contact betweenthe contact edge f of the pressure bar and the log or flitch.-Lv

With such a construction, during the sharpening operation, the' dull or nicked pressure bar, ltogether with ,its holder, are removedI as -a A`unit from. the latheorthe Vslic'er.v .At the grinding Wheel-theI pressure bar is adjusted with respect totheloca-ti-ngsurfaces on the holder toga dista'nceequal to the amount 'ofthe pressureA bar wh-ichv must 'b'e'ground away to produce 'a new perfect edge. The bevel ofthe pressure bar while rigidly/clamped in its holder, 'is vground until the distancefrcm vvtheinevf edgezto'the locating vsur- `faces onthe holder is the`correct distanceto bring the pressure bar contact edge to the proper position in the veneer lathe or slicer.' ,The pressure' bar 4and' pressure Ybar holder are' then removedfr'omihe grinder, and, due tothe suf-' cientlyl greatmoment of inertiav of the; pressure bar holderwith respect to the pressure'bar, `or 'in other Words, the Weight/of the pressure barholder withrespect to the press-ureibar, the contactfedge of the pressure b'arreinairis a straightfline and does not'bow orotherwise deflect'due to theinternalstres'se's'in the pressure bar. On're'pla'cing the resharpened pressure bar and its Aholdrin the'veneercutting or slicing machine soA that the locatingrsurfac'es'of the pressure barhc'lderrare infcontact with their cooperative locatingsurfaces in the veneer cutting machine, thepressure barisV automatically in correct''adjustment 'requiring nofurther manual local-adjusting.

`The invention `will lbe more lclearly understood from the following ldescription wherein:

'Figure 1 is the front elevation of afragmentary 4length "of the pressure bar and :pressure bar holder assembly? of this invention. F

` Figure 2..isa'transversesectionof the pressure4 barandk pressure l, barvholder ofl this invention Vtaken on lineair- 2 of' Figure k1, supported iin/a conventional mannerin a'veneerilathe'.

'Figure 3 is ay transversers'ection of the-pressure bar and pressure bar^liolder=1df-tliis` inventionY taken on line3-3 ofiFigur'el. Asshown in' the drawings pressure bar. holder 4f is:r an-a'ccurately machined rigid steelL-bea-m. Surfaces;5, `6, and-T1 ofthe"pressurehbar holder 4f'andthe cooperative abutting surfaces of-fthe 1 pressure bar holder carriager 8 rare accurately inacliined in parallelism-s0 that their entire/'length isparallel to the'aXis'ofrotation of the log `91 in aveneericutting lathe. `The pressure bar holder 4 'isi equippedv with avpluralityl of holes 'ill' 'each' of which accommodatesfaibolt-H'.4 Bolt Il is s`o threaded soV as to. be boltedito the internally and externally 'threaded'.bushing l2 Which -is *rigidly Afixed 'in pressurebar` holder carriages. Bolt Il x alscris eduippjed"wit-hi head :13hscconstructed to' -during the grinding operation-and4 another durrequirementsv of highlyfskilledtechniques;

j resharpens the pressure l,bar Yforcing the pressure bar,v by* Ylocal 1 adjustment, .to "assume-'a true 1 straight line. The grinder'then releases the v'pressure barY fromV the grinder carriage 'and' returns and pressurebar holder assembly isremovedfrom the `(pressure bar holder carriage 8 by loosening bolt ll thereby forcing the pressure bar and pressurebar holder-'jas a unit from the V4pressure ,bar holder carriage. `The pressure bar and pressure bar holder canfthenbe taken asa unit to v the grinding wheelfor grinding.` At thel grinding wheel, bolts I1 are loosened and by means ofbolts Y l5 and Ithe pressure bar 4I4 is so a fijusted and Y ground until the contact edge of pressure .bar I4 isatrue straight line and in parallelism withland at a predetermined distance from the locating surfaces 5 er1 of lthe-pressure barholder. 1n-

l-asmuchjas the pressure barv holder 4 has aisuffir- `cientmoment of inertia to resist deiiectionsof the pressure barV I4 dueto stresses and strains set up infthe pressure bar during the cutting and grinding operations, when the pressure bar holders which has been accurately aligned-at the grinding operation is repositioned inthe lathe, no further adjustment of pressure bar `I4 is required. .'Iherefore, vsince-the distance from the contact edge of `pressure bar I4 to locating surfaces 5 orl-'onthepressure bar holder is constant,'and since this; distanceis accurately set in Y, the grinding operation, and since these locating surfaces on-the pressure bar holder have accurately j-machined 'cooperative surfaces on the pressurebar holder carriage 8, allv that-remains after the'grinding operation is merely the seating Vof the pressure bar and pressure bar-"holder -assemblyV-in'the veneerlathe. Thus, instead of the procedure'as practiced heretofore ofirequiring ing theseating of thesharpened pressure bar Vin the lathe, only one alignment-'is necessary with the applicants invention greatly reducing Vthe According to heretofore practiced techniques,

machine. An experienced grinder then grinds. or

the lpressure. bar totheslicer or' veneer lathe.

Y However, on releasing thepre'ssure bar from the grind-er, dueto unbalanced stresses'in the pressure ba'r` and its 'lack of "rigidity, the true straight n:contact'edge vislos'tdue to deflections: Consequently, when thisA pressure bar-"isagainipositioned in the cuttinglatheiorfslicer, realignment -y into ya truef straight line. Such analigni-ng kand adjusting operation requires' afskilled craftsman.

With the pressure bar and pressure bar holder assembly of this invention, it is this second local adjustment of the pressure bar that is eliminated. Inasmuch as the contact edge has been properly aligned during the grinding operation and is rigidly held in place by a holder that has a suflicient moment of inertia to resist subsequent deections of the pressure bar and that such holder is so constructed with regard to the veneer cutting machine as to maintain a xed relationship between the line of c ontact of the contact edge of the pressure bar and the log or flitch, further adjustment of the pressure bar is unnecessary when the pressure bar and its'holder is repositioned in the veneer cutting machine.

What is claimed is: l

In a veneer cutting machine comprising an elongated pressure bar holder carriage, the improvement which consists in the provision of a combination pressure bar and pressure bar holder assembly of elongated form removable as a unit from the carriage, said holder being rela-` tively large in cross-section in relation to said pressure bar and having accurately machined locating surfaces adapted to abut accurately machined locating surfaces on the carriage to in- A sure close parallelism of the holder to the veneer cutting knife of the machine, push bolts adjustably threaded in the holder behind and abutting the bar at longitudinally spaced points for local adjustments of longitudinally spaced portions of the bar in the plane thereof, pull bolts in a plane parallel to the plane of the push bolts supported in holes provided in the holder and threaded in holes provided in the bar for local adjustments of longitudinally spaced portions of the bar in the plane thereof in the opposite direction to that of the adjustments afforded by said push bolts and other bolts rigidly securing the holder to the carriage.

ERICSSON H. MERRI'I'I.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 437,039- Oncken Sept. 23, 1890 458,717 Schwegman Sept. 1, 1891 835,156 Fitts r Nov. 6, 1906 1,957,166 Hartzell May 1, 1934 

